GB2160748A

GB2160748A - Graphic simulation system

Info

Publication number: GB2160748A
Application number: GB08512661A
Authority: GB
Inventors: Alan Lewis Stapleton
Original assignee: Micro Consultants Ltd
Current assignee: Micro Consultants Ltd
Priority date: 1984-06-22
Filing date: 1985-05-20
Publication date: 1985-12-24
Also published as: GB8416039D0; GB8512661D0; GB2160748B; US4766429A

Description

1

SPECIFICATION

Graphic simulation system This invention relates to a video graphic simulation system in which digital processing circuits generate or process electronically video signals which are capable of producing an image on a television type receiver.

A known form of such a system is one in which a store is provided forthe storage of separate signal elements which collectively represent a panoramic view, and the elements can be selectively read from said store in rasterformat and displayed on an image display device so thatthe panorama is that perceived from a particular position or direction determined by the rasterframe. This position or direction can be changed to simulate observations from a moving object by shifting the raster. With such a system a large panorama may be required to provide many different views and this may be very costly in storage, the video signals are usually provided in digital form and a very large density of digital words may be required overthe whole panorama. The object of the present invention is to provide a facilityfor producing panoramic views at less cost in storage than in previous systems.

According to the invention there is provided a video graphic simulator comprising (a) a video signal store having a multiplicity of storage locations for storing signal elements which collectively represent a panorama, (b) meansfor reading signalsfrom a rasterof said storage locations so that the view framed bysaid raster can be reproduced, (c) said means including viewselector means for selectively shifting said raster with respectto said storage locations sothatsaid frame can represent views from different directions or positions, (d)the arrangement being such thatsaid shiftcan causetheframeto project beyond the storage locations at leastatone edge and (e) said reading means are arranged tofill the projecting part oftheframewith video signals read from storage locations adjacentto the projecting edge.

The invention mayfind application, for example, when thefield of view is a seascape and it is desired to represent a change in viewfrom a rolling vessel.As thevessel rolls in one direction the amount of skywill increase. By repeating successive strips of sky atthe top edge of the picture as mirror images ofthe next stripthenthe amount of storage neededto produce the effect desired can be reduced. Conversely if the ship rolls in the other direction the amount of sky viewed will decrease and the effect of the increase in the amounts of sea seen can be produced by repeating 115 strips of the sea in the same way. A particular strip represented by signal elements in a number of lines (say 64) of storage locations can be "repeated" several times as the view changes. In cases where the image is GB 2 160 748 A 1 applicableto arrangements in which the image or images of an objectcan be superimposed onthe panorama andthe shifting of the rasterframe is arranged to follow the movementof one or more of the moving objects as described in ourco-pending patent application 8320357.

Sothatthe Invention may be more clearly under stood one example of this invention will be discussed with reference to the drawings:

Figure 1 represents a block diagram of this example.

Figure 2 represents an example of the final display on the screen with corresponding values of address bits.

Figure 3 comprises Figure 3(a) and Figure 3(b) representing examples of line addresses before de coding and after decoding.

Figure 4 represents the address bit decoder.

In Figure 1 the video signals representing the panoramic view are written into the frame store 9 from the disc store 5 at locations given bythe write address generator 6. The store 9 in this example has 512 lines of storage locations, each line includes 5120 storage locations. These components are all commercially known.Theview selector 12 can be controlled manually or automatically in responseto a computer and setsthe co-ordinates of one corner of the raster framewhich isto be displayed. This view selection is connected to two address generatorsoneof which (10) addressesthe pixels in a lineand otherofwhich 0 1) addresses the lines of the store. The lineaddress generator addresses the lines of video signals that are read from the store 9 to generate one frame of display.

The position of these lines will determine the vertical position in view. The pixel address generator gener ates the horizontal addresses in the storage locations from which video signals are taken to form each line.

These lines can shift horizontally so that a horizontal change in the field of view can be represented. The invention is primarily concerned with the shift in the vertical position of the frame and the rest of the discussion will be confined to the operation of the invention with respectto this. The rasterframe of video signals chosen by the view selector can be displayed on the display device 8 after being con verted to analogue signals in the digital to analogue converter7.

In Figure 2 references 21 and 22 respectively representthetop and bottom lines of storage loca tions in the store 9 and maythus be said to represent the top and bottom edges of the store. The two lines arethusthefirst line and 512th line of the store (address 0 and address 511). In operation the address generator generates line addresses in the store 9 from which video signals are to be read to form the display in the display device. The store line addresses are generated in the time order in which respective lines are displayed bythe display device. If the vertical such that repeating sections without mirroring would 120 position of the displayframe, as determined by view produce no noticeable discontinuities the mirroring maybe omitted. Since the sea and sky maybe amorphous or have irregular texture the effect of "mirroring" may hardly be nOtiGeabe. The invention is selector 12, is central, so that it does not project beyond line 21 and 22 video signals will be read from the lines of store 9 in normal order beginning with the first line and ending with the 512th line with due The drawing(s) originally filed was(were) informal and the print here reproduced is taken from a later filed formal copy.

2 GB 2 160 748 A 2 regardto interlacing. If howeverthe displayframe projects,say, abovethetop edge of the storethe projecting partof the displayframe hasto befilled by lines of video signal read from the store 9 outof normal order.Theframe of coursewill befilled before the reading process reachesthe bottom edge 22 of the storeg. Similarlyif thedisplayframe projects below the bottom edge 22 of the store, reading from the store will start at some line of the store below top edge 21, whilstthe projecting part of theframe will be filled by lines of video signal read from nearthe bottom of the store out of normal order.

The address generator 11 is programmed to operate in such a way that if view selector indicates, say, that the reading frame projects say by 64 lines above the top edge of the store 9 the projecting frame is filled by addressing first line 63 of the store 9, then addressing line 62 and so on in reverse order down to line 0.

Thereupon address generator re-addresses line 0, then line 1 and so on in normal order down to line 447, 85 whereupon the displayframe isfilled. ltwill be understood of course that if there is interlacing the odd and even lines will be addressed in alternate field periods. If the extent of the projection of the display frame beyond top edge 21 is say 128 lines, the first address generated by the generator 11 is line 0 of the store,thenlinel andso on upto line 63, then 62,61 etc:

are addressed. That is to sayto fill the projecting part ofthe storethetop 64 lines of thevideo signals in the store 9 are mirrored as manytimes as required to fill the frame. The situation is similar if frame projects beyond the bottom edge 22.

In Figure 2there isshown on the right, partof the address generated by the address generator to denote particular lines of the store, depending on the output 100 of the view selector. Some complete addresses are shown in Figure 3. Each fine address is a digital word of 11 binary digits and the two highest digits V9 and V1 0 are used to indicate whether or notthe display frame projects beyond the top or bottom edges of the 105 store 9, whereas the remaining eight digits VO - V8 denote actual lines of the store 9.When V9 and V1 0 are both 0 the remaining digits V8 - VO denote the store linesO-511 in a conventional way. The lines above the top edge are given negative numbers and so if V9 and 110 V10areboth 1, this denotes that the display frame projects beyond the top edge of the store; the remaining digits V8 -VO again denote respective store lines but according to a special convention. Similarly, ifV10 isO and V9 is 1, projection beyondthe bottom edge of the store is indicated and the remaining digits denote respective store lines according to another special convention. Value of the other digits VO - V5 are not indicated in Figure 2 it is believed thattheywill be apparent (from the description) to a person skilled in the art.

To illustrate the address coding Figure 3(a) indicates the addresses which will be generated bythe address generatorforthe first line (the topmost line in the actual images as views) of the display frame when the 125 frame projects beyond the top edge 21 by 1, 2,64,65 and 66 lines respectively. It is considered thatthe coding forthe other lines will readily be appreciated. Figure 3(b) shows the corresponding decoded addres- ses forthe store lines for projections of 1, 2 and 64 lines, the said store line addresses now being 0, 1 and 63 in conventional binary as required. The convention for decoding is that digits V6 - V8 are forced to value 0, if not initially 0, and that if V6 is initially 1, digits VO -V5 are inverted. If the displayframe project more than 128 lines abovethetop edge of the store, digit V7 becomes 0, and if it projects morethan 256 lines, digitV8 becomes 0. The display frame may project more than 512 lines abovethetop edge of the store in which case V9 will becomezerc4 and the decoding will proceed as before. Addresses inthe casewhere the displayframe projects beyondthebottom edge 22 are generated in a similar mannerthe decoding convention in this case being, however, thatV6 -V8 areforced to value 1, and that if V6 is initially 0, VO -V5 are inverted. If the display frame projects more than 64,128,256 lines belowthe bottom edge of the store, the digits V7, V7 and V8 change in value accordingly.

The decoding process in the address generator can be seen more clearly in Figure 4-As stated before if the rasterframe project above the store the digit V1 0 is set to one, because the addresses are negative and V9 maybe one or zero. In the decoderthis is decoded at 30, this activates the circuit 25 which sets V6 to V8 to zero. If V6was originally 1 when the value of V1 Owas 1 then this is detected at 28 and the AND gate 31 which later produces an output which actives an inverting circuit 26 and VO to V5 are inverted. This gives the projections at the top of the store. When the raster frame is not projecting from the store, V10 and V9 are zero which is detected at29 and all the address digits are read as normal, inverting circuit 26 being transparent. If the raster frame projects at the bottom of the storethenvaluesof V1OandV9areO and 1 respectively. This condition activates gate 27 which setsV8to V6to a value of 1 in circuit32 and again the value of V6 is used to produce the mirroring of the lines. If V6 is originally zero this is decoded at33 and the AND gate 34 produces an output which activates the inverting circuit 26. The lines are then written onto thescreen reverse order compared to the next strip. Bythe use of such a decoding method the desired projection effects may be achieved.

Several variations of the present invention are envisaged. The address generatorcould be such that the video signals used to fill a projecting frame could be taken from a portion ofthe store lines not included in the frame. The systemcouldalso be adapted so that the projecting edge wasavertical one and by mirroring pixels instead of linesthe display could be extended sideways. The video signals used to fill the projecting frame ofthe store may in some cases be taken from storage locations not close to the edges of the store. Mirror imaging of the lines used to fill the projecting frame may be dispensed with in some cases.

Claims

Afurther variation is in the size of the rasterframe defining the view selected. This may be such thatthe frame always projects across one or both edges of the store. In one example the frame is 576 lines deep and so 64 lines of the store need to be repeated even when the frame is central, 32 at the top and 32 atthe bottom. CLAIMS

1. A video graphic simulator system comprising; video signal store means having a multiplicity of 3 GB 2 160 748 A 3 storage locations forstoring signal elementswhich collectively represent a panorama, meansfor reading signalsfrom a raster of said storage locations so that the view framed bysaid rastercan be 5 reproduced, viewselector meansfor selectively shifting said raster with respectto said storage locations sothat said frame can represent views from different directions or positions,the arrangement being such thatsaid shift can causetheframe to project beyondthe storage locations at least at one edge and said reading means include meansto fill the projecting part of theframe with video signals read from the storage locations adjacentto the projecting edge.

2. Avideo graphic simulator system as claimed in Claim 1, wherein said reading means further includes address generating means to generate the addresses ofthe video signals to be used to fill the projecting part of the frame, said address generating means being controlled by said view selector means.

3. Avideo graphic simulator system as claimed in Claim 2, wherein said view selector means are operator controlled.

4. Avideo graphic simulator system as claimed in Claim 3, wherein said address generating means includes means for determining the position of the projecting edge with respectto the store, said address generating means being arranged to generate the addresses of the video signals to be read to f ill the projecting part of the frame in response to the determined position of the edge.

5. A video graphics simulator system as claimed in Claim 4. wherein said address generpting means generates addresses such thatthe plurality of lines of video signals are read to fill the projecting part of the frame in such a manner asto produce a mirror image of that represented by the next plurality of lines.

6. A method of video graphic simulation comprising; storing in a plurality of storage locations video signals representing a panorama, selecting a rasterof video signals from storage locations so thatthe view in said raster can be reproduced, selectively, moving said rasterwith respectto said storage locations so thatthe view seen may be changed, said movement being such thatthe raster may project beyond the Store at least at one edge, and reading video signalsfrom said storage locations to fill the projecting part of said raster.

7. A method as claimed in Claim 6, further comprising the step of reading a plurality of lines of video signals from said store so that the image represented by said lines is the mirror image of that represented bythe next plurality of lines.

8. A video graphics simulator system substantially as described herein with reference to the accompanying drawings.

Printed in the United Kingdom for Her Majesty's Stationery Office, 8818935, 12185, 18996. Published at the Patent Office, 25 Southampton Buildings, London WC2A lAY, from which copies may be obtained.